Bug: _get_provider_base_url() crashes when providers is defined as a list in config.yaml

[Fillaus]

Bug: _get_provider_base_url() crashes when providers is defined as a list in config.yaml

Description

The function _get_provider_base_url(provider_id) in api/config.py (line ~1921) assumes that cfg["providers"] is always a dict. When the user defines it as a list instead (providers: []), the function crashes with:

AttributeError: 'list' object has no attribute 'get'

Reproduction

1. In config.yaml, set: providers: [] (empty list)
2. Start a chat that triggers _get_provider_base_url()
3. Result: AttributeError: 'list' object has no attribute 'get'

Root Cause

The line:

prov_cfg = cfg.get("providers", {}).get(provider_id, {}) or {}

only works with a dict. An empty list [] is semantically identical to {} ("no providers configured"), but the code doesn't handle both forms.

Fix

def _get_provider_base_url(provider_id):
    """Look up the configured base_url for a provider (e.g. lmstudio).

    Checks two locations, in order:
      1. ``cfg["providers"][<provider_id>]["base_url"]`` — the explicit
       per-provider override.
      2. ``cfg["model"]["base_url"]`` — falls back here when
       ``cfg["model"]["provider"] == provider_id``. This is the historical
       shape (the model block carries both the active provider AND the
       base URL for that provider in a single record).

    Returns the URL stripped of trailing ``/`` if configured, otherwise None.
    """
    prov_raw = cfg.get("providers", {})
    # providers can be a dict (provider_id -> config) or a list of provider entries
    if isinstance(prov_raw, dict):
        prov_cfg = prov_raw.get(provider_id, {}) or {}
    elif isinstance(prov_raw, list):
        # Search for matching provider in list format
        prov_cfg = None
        for entry in prov_raw:
            if isinstance(entry, dict):
                entry_id = str(entry.get("id", "") or entry.get("name", "")).strip().lower()
                if entry_id == str(provider_id).strip().lower():
                    prov_cfg = entry
                    break
        prov_cfg = prov_cfg or {}
    else:
        prov_cfg = {}
    explicit = (prov_cfg.get("base_url") or "").strip().rstrip("/")
    if explicit:
        return explicit
    model_cfg = cfg.get("model", {}) or {}
    if isinstance(model_cfg, dict):
        model_provider = str(model_cfg.get("provider") or "").strip().lower()
        if model_provider == str(provider_id).strip().lower():
            model_base = (model_cfg.get("base_url") or "").strip().rstrip("/")
            if model_base:
                return model_base
    return None

Background

The bug has existed since commit 35cf332c ("feat: add LM Studio provider support with live model discovery"). Since then, 125+ commits touched config.py, but no one caught the list-form edge case.

Most users either have {} or don't set providers explicitly at all. Only in rare cases is a list used — and then the chat crashes.

[nesquena-hermes]

Thanks for the detailed report and the proposed patch — the crash is real, and I can pin it down precisely. A couple of nuances change the recommended fix, though.

Code reference

Reading api/config.py:1908-1921 on origin/master, the offending line is:

def _get_provider_base_url(provider_id):
    ...
    prov_cfg = cfg.get("providers", {}).get(provider_id, {}) or {}

When config.yaml has providers: present with a list value, cfg.get("providers", {}) returns the list (the {} default only applies when the key is absent), so [].get(provider_id, {}) raises AttributeError: 'list' object has no attribute 'get'. Confirmed.

Diagnosis

Two things worth knowing before patching:

1. Your exact repro (providers: [], empty list) is already fixed on an open PR. PR #3967 (fix/config-none-providers) rewrites this exact line:

prov_cfg = (cfg.get("providers") or {}).get(provider_id, {}) or {}

An empty list is falsy in Python, so [] or {} → {}. Once #3967 merges, providers: [] will resolve to {} and stop crashing — a plain git pull will pick it up. So the empty-list case doesn't need a separate fix.

2. A non-empty list would still crash even after #3967, because [{...}] or {} is truthy and returns the list, so .get() fails again. That's the residual gap your patch is reaching for.

The thing is, providers is a dict keyed by provider_id everywhere else in this file — every other call site already guards with isinstance(providers_cfg, dict):

api/config.py:2254   provider_specific = providers_cfg.get(pid, {}) if isinstance(providers_cfg, dict) else {}
api/config.py:4228   if isinstance(providers_cfg, dict):
api/config.py:4422   if isinstance(providers_cfg, dict):
api/config.py:4594   only_show_configured = providers_cfg.get("only_configured", False) if isinstance(providers_cfg, dict) else False

The list-of-entries shape your patch searches (entry.get("id") / entry.get("name")) is actually the shape of custom_providers (see api/config.py:4240, 4463), not providers. So adding list-search logic here would silently accept a malformed providers: block rather than treating it as "nothing configured", and it'd diverge from the rest of the file.

Recommendation

For full hardening (covering the non-empty-list case #3967 doesn't), match the canonical guard instead of list-search:

prov_raw = cfg.get("providers")
prov_cfg = prov_raw.get(provider_id, {}) if isinstance(prov_raw, dict) else {}
prov_cfg = prov_cfg or {}

This collapses both None, [], and any non-dict to {} ("no providers configured") in one line, consistent with lines 2254/4228/4422/4594.

Verification

• With providers: [] → resolves to {}, falls through to the cfg["model"]["base_url"] branch, returns None if unset. No crash.
• With a non-empty list → same, treated as unconfigured.
• With the normal dict shape → unchanged behavior.

If you're only hitting the empty-list form, #3967 already covers you today. If you want the non-empty-list case closed too, the isinstance guard above is the minimal addition.

[nesquena-hermes]

Shipped in v0.51.362 (Release MA) via #4008 — malformed providers config now treated as unconfigured (isinstance-guarded) instead of crashing. Thanks @rodboev. Codex SAFE, suite 8626, deployed.